1. Field
The present invention relates generally to light diffusing optical fibers having a region with nano-sized structures, and in particular to illumination systems and methods that employ such fibers for different applications including bioreactors, signage and special lighting applications.
2. Technical Background
Optical fibers are used for a variety of applications where light needs to be delivered from a light source to a remote location. Optical telecommunication systems, for example, rely on a network of optical fibers to transmit light from a service provider to system end-users.
Telecommunication optical fibers are designed to operate at near-infrared wavelengths in the range from 800 nm to 1675 nm where there are only relatively low levels of attenuation due to absorption and scattering. This allows most of the light injected into one end of the fiber to exit the opposite end of the fiber with only insubstantial amounts exiting peripherally through the sides of the fiber.
Recently, there has been a growing need to have optical fibers that are less sensitive to bending than conventional fibers. This is because more and more telecommunication systems are being deployed in configurations that require the optical fiber to be bent tightly. This need has lead to the development of optical fibers that utilize a ring of small non-periodically disposed voids that surround the core region. The void containing ring serves to increase the bend insensitivity—that is to say, the fiber can have a smaller bend radius without suffering a significant change in the attenuation of the optical signal passing through. In these fibers the void containing ring region is placed in the cladding of the optical fiber some distance from the core in order to minimize amount of the light propagation through void containing ring region, since it could increase optical loss.
Because optical fibers are typically designed to efficiently deliver light from one end of the fiber to the other end of the fiber over long distances, very little light escapes from the sides of the typical fiber, and, therefore optical fibers are not considered to be well-suited for use in forming an extended illumination source. Yet, there are a number of applications such as special lighting, signage, or biological applications, including bacteria growth and the production of photo-bioenergy and biomass fuels, where select amounts of light need to be provided in an efficient manner to the specified areas. For biomass growth there is a need to develop processes that convert light energy into biomass-based fuels. For special lighting the light source needs to be thin, flexible, and easily modified to variety of different shapes.